periodic table

• elements are arranged in vertical columns called groups
• each element in a group has atoms with the same number of outer-shell electrons and similar properties
• the elements are arranged in horizontal rows called periods
• the number of the period gives the number of the highest energy electron shell in an elements atom
• periodicity 


  a repeating trend in properties of the elements across each period
• s block

  group 1 and 2
• d block

  transition metals
• p block

  groups 3-8